When choosing plants for your garden, it's important to know whether you are buying an example of the true native species, or some cultivated form. Here is a quick tutorial.
Click on the thumbnail below to download or print this handy reference guide:
Before I get into the different terminology, let's take a quick detour to discuss botanical nomenclature. Those long, hard-to-pronounce Latin names can seem unwieldy or difficult to remember, but it is always useful to be familiar with them whenever you can. Common names can be confusing because more than one plant might share the same common name, or one plant may have several different common names. Additionally, common names don't give a sense of the relationship between plants, so they are less helpful when trying to understand plant characteristics, habits, and preferences.
Briefly, when you see a botanical name written for a species, it always has two words, written in italics, like this:
The first word, always capitalized, is the genus. The second word, in lower case, is the specific epithet. Written together, you have the species.
There are many different species of Symphyotrichum (which are the asters): Symphyotrichum oblongifolium, Symphyotricum novae-angliae, Symphyotrichum laeve, etc. They are closely related, so they share the same genus. In writing, once a full binomial name has been mentioned, thereafter, the genus may be abbreviated, to become S. oblongifolium, S. novae-angliae, S. laeve.
Sometimes there are more than two italicized Latin words, like this:
Persea borbonia var. pubescens
Sarracenia rubra ssp. gulfensis
In these cases, the "var." and "ssp." abbreviations are lower case and not italicized. They stand for variety and subspecies. The variety or subspecies name is italicized and usually lower case.
(Just to make it more confusing, you might run across the abbreviation "sp.", which means species, and "spp." which is the abbreviated plural form of species.)
Sometimes, there are additional un-italicized words in single quotes, like this:
Symphyotrichum oblongifolium 'October Skies'
In this case, 'October Skies' is the cultivar name. It is always in single quotes and un-italicized, and usually capitalized.
Why does this terminology matter?
There are a number of reasons why it is helpful to understand botanical terminology:
You get a deeper understanding of how plants are related to each other, and learn to recognize similar plants.You can communicate about plants with anyone, anywhere in the world. Botanical names are used globally, so even if you don't know the French word for "flowering dogwood," you can say "Cornus florida," and a French person will know exactly which plant you mean (assuming that they are also familiar with botanical nomenclature and that species, of course!).When purchasing plants, you can tell whether you are buying an example of the species, or some variation. Furthermore, you will understand the nature of that variation, and can decide whether to include it in your landscape or keep looking for the plant you want.
Species, Straight Species, and Local Ecotype Native
A single species has a binomial (two-part) name, like Symphyotrichum oblongifolium. This is sometimes referred to as the "straight species." It is how the plant grows in the wild. If you collect and plant its seeds, they will grow "true to type," or appear similar to the parent plant. Open pollinated seed propagation of a species will preserve the natural genetic diversity in the population, because genes from different plants are allowed to mix and mingle as they do in nature.
Genetic diversity is important because it helps to protect the natural biodiversity of life on the planet. One way in which we see the benefit of genetic diversity is when a widespread disease threatens a species.
Of all of the Ulmus americana (American elm) trees in North America, most succumbed to Dutch elm disease in the twentieth century. A relative few, however, were resistant due to natural variations in their genetics. Scientists have identified certain trees with genetic resistance, and have been working to breed a new population of disease-resistant elms.
If you start down the path of using more native plants, you might come across the term "local ecotype native." This simply refers to plants that belong to the species, but which originated within your local area or ecosystem (a.k.a. ecoregion). Some native plant proponents believe that this level of specificity can be important, arguing that a Symphyotrichum oblongifolium that originated from a nearby meadow will be more likely to support your local insects and wildlife, due to various adaptations over time. As such, it will likely perform better in your landscape, and will support the genetic diversity of that species within your ecoregion.
A subspecies is a naturally occurring, distinct variant of a species, usually from a particular geographical region. It is different enough so as to be distinguishable from the ordinary species, and stable enough to reproduce the distinguishing characteristics over generations. Seedling offspring will usually grow true to type.
A variety is a distinct variant of a plant that occurs in nature due to a genetic mutation. It may have a different color flower, or thinner leaves, or some other distinguishing characteristic(s) that makes it slightly different from the species. When propagated by seed, the offspring will usually grow true to type.
Cultivars: Selections and Nativars
A cultivar is a cultivated variety. It is a distinct variant of a plant that has been intentionally cultivated by humans. Cultivars are often selections, meaning that someone breeding plants noticed a variant and then intentionally selected and bred that variant for its compact size, large bloom size, or different leaf color (for example). Cultivars can occasionally include naturally occurring mutations discovered and propagated by people. They can also include variants that have been genetically engineered. You can always identify a labeled cultivar by the un-italicized words following the specific epithet, e.g., Symphyotrichum oblongifolium 'October Skies'.
When propagated by seed, cultivars sometimes but not always grow true to type. As a result, most cultivars found in nurseries and plant catalogs are vegetatively, or clonally propagated. This means that they have been grown from cuttings, divisions, or tissue culture, and are genetically identical to the parent plant. Therefore, the species's natural genetic diversity is not preserved for two reasons: first, because a distinct variant is being reproduced, rather than the ordinary species, and second, because genes are not mixing during reproduction.
A nativar is a cultivated variety of a native species. This is a rather ambiguous term, because "native" is relative. Thus, if you live in, say, Missouri, then Symphyotrichum oblongifolium 'October Skies' could be called a nativar, but if you live in California, it cannot, since that plant occurs naturally in the Midwest, but not on the west coast.
Cultivars also include hybrids, which are typically crosses between two different species. Usually, hybrids are bred intentionally by humans, although they can occur naturally as well. Hybrids can also be made between two different genera, although it is rarer, due to the genetic incompatibility that usually distinguishes one genus from another. Finally, hybrids can also be made between subspecies, varieties, and cultivars.
Hybrids are identified with an "x" in their name to indicate crossbreeding, as in: Lavandula x intermedia, or Lavandula x intermedia 'Phenomenal'. Lavandula x intermedia is known as Lavandin, and is a cross between English lavender, Lavandula angustifolia, and Portuguese lavender, Lavandula latifolia. 'Phenomenal' is a particular hybrid cultivar.
A word on patented plants. Individuals or companies have the ability to acquire patents for cultivars (selections or hybrids). Plant patents last for a minimum of 20 years, and give the patent owners sole rights to use, manufacture, breed, and propagate the cultivar. You will be able to identify a patented plant if you see a number after the botanical name, such as: Daphne x transatlantica 'BLAFRA' Plant Patent #18,361. Sometimes you will see the abbreviation PP (Plant Patent) or PPAF (Plant Patent Applied For). A patent is a form of intellectual property rights. Its intent is essentially to protect the owner's investment of time and resources into the development of the cultivar.
Legally speaking, you are not allowed to take a cutting or division from a patented plant and propagate it, even on your own property. However, you are unlikely to be found out, and extremely unlikely to be prosecuted for doing so. However however, it is certainly against the spirit and letter of the law to propagate and sell your cuttings/divisions. So don't sell them.
A trademark is a designation protecting a cultivar's commercial name, and is indicated by the symbols ® or ™, for example, the Wave® Petunia series. It is a way to build brand loyalty. Only the name is protected, rather than the cultivar itself. Thus, you are allowed to take cuttings or divisions of a trademarked plant (unless it is also patented), and even resell it, but you may not call it "Wave."
That's it in a nutshell. I hope this clarifies some of the naming conventions and terms used in the plant industry. Please let me know in the comments below if you found this useful, or have additional thoughts on the topic.